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Monthly Archives: December 2014

To get a good look at the impacts of global warming, you may need to look no farther than your own yard. Some unexpected species may perch in a local tree or stop by your bird feeder. These newcomers have been lured north by winter’s warmer temperatures, a new study finds. Birds such as cardinals and Carolina wrens are now wintering farther north than they did as little as 20 years ago.

Since 1970, the average winter low temperatures have risen by about 0.38 degree Celsius (0.68 degree Fahrenheit) in eastern North America. Global warming, also known as climate change, is the cause.

For several decades now, the planet has been slowly warming. The world’s animals and plants have responded. Many have begun to move north or south to keep pace with the conditions they’re used to. Such movement is considered one of the best fingerprints of climate change.

Benjamin Zuckerberg and Karine Princé are wildlife biologists at the University of Wisconsin-Madison. They wanted to look for evidence that Earth’s warming had been affecting bird behaviors — such as where they settle for the winter. To do this, they analyzed two decades of data from a program called Project FeederWatch. This citizen-science project at the Cornell Lab of Ornithology in Ithaca, N.Y., collects reports of sightings at bird feeders from early November to late April.

There are currently more than 10,000 participating sites in the United States and Canada. Many of the studied feeders sit in people’s yards.

For the project, volunteers have been identifying and counting birds at a feeding station for two-day periods throughout the winter. Zuckerberg and Princé focused on data from 1989 to 2011 at sites in eastern North America. They limited their analysis to reports from the “core winter” period: December 1 to February 8. For each site, the researchers tracked down the yearly average low temperature for that core period. The northern boundary for many North American birds is determined by that minimum winter temperature. The scientists restricted their counts to 38 of the more common species.

From the 22 years of data that they mined, the scientists detected a gradual increase in the minimum winter temperatures. Over that time, the birds didn’t all collectively begin moving northward. But many warm-adapted species began to spend the colder months of the year farther north, the data show. Warm-adapted birds are species that decades ago wintered solely in the South.

“The winter bird communities of eastern North America are increasingly dominated by warm-adapted species,” the researchers note. Some areas of the North now host wintering Carolina wrens, cardinals, purple finches, eastern bluebirds or red-bellied woodpeckers.

This Baird’s sparrow was photographed in 2013 near the Rattlesnake Springs Picnic Area in Eddy County, N.M. The species could be driven out of the country by 2075, says a new study.

NICHOLAS PEDERSON/FLICKR (CC BY-NC-SA 2.0)

The birds are getting an assist from the feeders that people keep full throughout the winter. But Zuckerberg and Princé don’t think the seeds that people are supplying account for the change in the birds’ ranges. Indeed, the number of bird feeders in the United States has changed little since 1991. Throughout, the total has hovered at around 53 million.

Habitat loss could be driving some change in where various bird species spend the winter. But habitat changes — such as cutting down forests or paving over fields — tend to be local. The observed change in where birds are wintering, by contrast, has been seen across eastern North America. The researchers conclude that climate change is the most likely cause.

The movement of certain species may prove to be a positive trend for some of the species. But that’s not been confirmed yet. And scientists can’t assume that the species that move northward will not encounter problems. The shuffling of bird communities “could alter the interactions between bird species, possibly with some northerly species being outcompeted by new arriving species,” Princé says. That may lead to the formation of new communities of birds that didn’t exist in the past. Scientists don’t yet know what those communities will look like, or how the birds will interact with each other. “We still have to explore the consequences of such changes.”

And more community shuffling may be in the birds’ future, according to a study published November 5 inPLOS ONE. Terry L. Sohl of the U.S. Geological Survey in Sioux Falls, S.D., looked at what might happen to 50 U.S. bird species by 2075. He found that many would change where they live because of global warming and because of changes in how land is used. Some species, such as the cactus wren and Gambel’s quail, would have more land suitable for them to live on. But others, such as the Baird’s sparrow, could be driven out of the country.

Power Words

citizen science Scientific research in which the public — people of all ages and abilities — participate. The data these citizen “scientists” collect help to advance research. Letting the public participate means that scientists can get data from many more people and places than would be available if they were working alone.

climate The weather conditions prevailing in an area in general or over a long period.

climate change Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.

global warming The gradual increase in the overall temperature of Earth’s atmosphere due to the greenhouse effect. This effect is caused by increased levels of carbon dioxide, chlorofluorocarbons and other gases in the air, many of them released by human activity.

habitat The area or natural environment in which an animal or plant normally lives, such as a desert, coral reef or freshwater lake. A habitat can be home to thousands of different species.

There’s an old saying about enemies: If you can’t beat ‘em, join ‘em. Evolution provided one type of dinosaur with a slightly different message: If you can’t beat ‘em, run!

Many dinosaurs had some type of defense against predators. Stegosaurs had spikes on their tails.Triceratops and its relatives had horns. Some species of the long-necked dinosaurs known as sauropods evolved to be so large that predators couldn’t successfully attack a healthy adult.

But hadrosaurs, commonly known as duck-billed dinosaurs, seemingly had no such defenses. Fossils suggest that they had no armor, no spikes and no horns. And they were about the same size or smaller than tyrannosaurs, their main predators.

Yet hadrosaurs undoubtedly were successful, notes Scott Persons. He works at the University of Alberta in Edmonton, Canada. As a vertebrate paleontologist there, he studies the fossils of creatures that had backbones. In many places in Asia and North America, he points out, hadrosaur fossils outnumber those of all other large dinosaurs combined.

Hadrosaurs usually walked on all fours. Still, they likely ran using only their big hind legs. The muscle arrangement in those hind limbs likely helped them outrun predators such as T. rex.

NOBU TAMURA/WIKIPEDIA COMMONS

Clearly, he concludes, “Hadrosaurs had to be doing something right.” But how did these plant-eaters, which possessed no apparent defenses, survive in a landscape full of big-toothed predators?

That’s a very good question, says Persons. To tackle this mystery, he teamed up with Philip Currie to study the well-preserved fossils of two hadrosaurs. Both had been unearthed in Alberta. They came from rocks that are roughly 75 million years old. One set of fossils came from an adult. The other dino had not yet fully grown up.

In general, a hadrosaur’s body resembled that of a tyrannosaur. Although a hadrosaur typically walked on all fours, it likely ran using its hind legs only. Tyrannosaurs were bipedal, meaning they moved solely on two legs. Both types of dinosaur relied on a big leg muscle called the caudofemoralis (CAW-doh-fem-or-AAH-lis).

That muscle gets its name from where it attaches to the skeleton, Persons explains. The upper end is connected to bones in the base of the tail. (In Latin, caudum means tail.) The lower end of the muscle is attached to the femur (FEE-murr), the large bone in the upper leg. When this big muscle contracted, it pulled the leg backward. That, in turn, propelled the animal forward.

But there was one key difference between tyrannosaurs and hadrosaurs: precisely where that big muscle attached to the femur.

In tyrannosaurs, it connected to the upper part of that leg bone. With one quick contraction of this muscle, the meat-eater could have made a long sudden stride. That’s a great benefit for a predator trying to ambush its prey. But being attached high on the femur also provided little leverage, says Persons. That means the tyrannosaur’s stride wasn’t very efficient. So, a run likely tired this hunter relatively quickly. You might therefore think of these beasts as sprinters.

In hadrosaurs, that big muscle attached much lower on the femur. That required a longer muscle. And it would have contracted more slowly than in the tyrannosaur. So the hadrosaur wouldn’t have been much of a sprinter, Persons says. But the muscle’s lower femur attachment would have given it more leverage. That would have made the hadrosaurs’ strides more efficient. So these prey shouldn’t have tired nearly as quickly as their hunters.

In other words, the big plant-eater may have started running relatively slowly but probably would have been able to run for far longer than a tyrannosaur. So, if a hadrosaur escaped an initial ambush, it might have stood a good chance of outrunning its predator, Persons and Currie now conclude. Their analysis was published November 5 as part of a 36-chapter book on hadrosaurs.

The muscle attachment (broad bump) on a hadrosaur’s femur (bone A, at left) is farther down on the bone than it is on a tyrannosaur (bone B, at right). That longer distance (blue arrow vs. red) would have given the hadrosaur more efficient strides. That, in turn, would have provided the endurance to outpace a predator in the long run.

W.S. PERSONS IV AND P.J. CURRIE

“These results seem quite reasonable,” says Thomas R. Holtz, Jr. Tyrannosaurs were well adapted for speed, notes this vertebrate paleontologist at the University of Maryland in College Park. But in the long run, “endurance would have given a hadrosaur the ability to outrun a tyrannosaur,” Holtz says. “If an attack couldn’t be avoided, then running was probably their best bet.”

The analysis by Persons and Currie “is a good solid preliminary study,” says Philip Manning. He’s a vertebrate paleontologist at the University of Manchester in England. He agrees that hadrosaurs probably had an advantage in long-distance running. But these dinosaurs also had a leg up on tyrannosaurs in other ways, he suspects.

Previous studies have bolstered the idea that hadrosaurs lived in large herds. With so many eyes and ears alert at the same time, it would have been difficult for a predator to sneak up on an entire herd. “That sort of behavior would be as good as any armor plate,” Manning suggests.

Holtz agrees: By traveling in large groups, he notes, one individual hadrosaur might be lost in a predator’s attack, but the rest of the group would survive.

Power Words

bipedal An adjective to describe an animal that walks on two feet.

caudofemoralis A muscle found in many creatures with a tail. It takes its name from the body parts to which its ends attach. In Latin, caudum means tail and femur means thighbone.

Cretaceous Period A geologic time period that included the end of the Age of Dinosaurs. It ran from roughly 145.5 million years ago until 65.5 million years ago.

dinosaur A term that means terrible lizard. These ancient reptiles lived from about 250 million years ago to roughly 65 million years ago. All descended from egg-laying reptiles known as archosaurs. Their descendants eventually split into two lines. They are distinguished by their hips. The lizard-hipped line became saurichians, such as two-footed theropods like T. rex and the lumbering four-footed Apatosaurus(once known as brontosaurus). A second line of so-called bird-hipped, or ornithischian dinosaurs, led to a widely differing group of animals that included the stegosaurs and duck-billed dinosaurs.

femur In humans, the large bone in the upper leg. It is commonly known as the thighbone. In tetrapods (creatures with four limbs), it’s the large bone in the upper hind limbs.

fossil Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils.

hadrosaur A duck-billed, plant-eating dinosaur that lived during the late Cretaceous Era.

paleontologist A scientist who specializes in studying fossils, the remains of ancient organisms.

predator (adjective: predatory) A creature that preys on other animals for most or all of its food.

prey Animal species eaten by others.

stegosaurs Plant-eating dinosaurs that had large, protective plates or spikes on their backs and tails. The best known: Stegosaurus, a 6-meter (20-foot) long creature from the late Jurassic that lumbered around the Earth some 150 million years ago.

tetrapod A four-limbed animal, including amphibians, reptiles, birds and mammals.

tyrannosaur A line of meat-eating dinosaurs that began during the late Jurassic Period, about 150 million years ago. These species persisted into the late Cretaceous Period, about 65 million years ago. The best known member of these species: the late Cretaceous’ Tyrannosaurus rex, a 12-meter (40-foot) long top predator of its time.

vertebrate The group of animals with a brain, two eyes, and a stiff nerve cord or backbone running down the back. This group includes all fish, amphibians, reptiles, birds and mammals.

WASHINGTON, D.C. — The minty flavor added to menthol cigarettes might make it even harder for smokers to quit, new research shows.

Most smokers know they should quit. Unfortunately, the nicotine in tobacco is addictive. That makes quitting really hard. Scientists have known that it’s even harder for people who light up menthol cigarettes.

The question has been why, notes Brandon Henderson. He’s a neuroscientist in Pasadena at the California Institute of Technology, or Caltech.

The answer, his team now finds, may have a lot to do with how menthol boosts the effect of nicotine on the brain. Repeated exposure to nicotine leads the brain to make more nicotine receptors — docking stations for the chemical on cells. These nicotinic receptors are proteins. And their role is to impact the brain’s pathways for a chemical known as dopamine (DOPE-uh-meen). Dopamine transmits signals in the brain. Some of those signals turn on centers that convey feelings of pleasure and rewards. Indeed, this feel-good chemical helps make smoking rewarding — and addictive.

To see how menthol might affect this system, Henderson and his Caltech teammates worked with special lab mice. One type of nicotinic receptor in the mice glows cherry red under fluorescent light. Another type glows bright green.

The researchers exposed these mice to menthol. (This chemical occurs naturally in spearmint and peppermint.) Then the experts focused in on a part of the midbrain. It’s known as the ventral tegmental area, or VTA. The VTA plays a role in emotion, motivation and addiction.

Mice exposed to menthol had more of both types of nicotinic receptors than did unexposed mice. The increase was similar to that produced by nicotine, the scientists found.

“This goes to show that menthol is not simply an inert flavoring in cigarettes,” says Henderson. “It has some effects in the brain.” Henderson presented his team’s results here on November 16 at the annual meeting of the Society for Neuroscience.

“The most significant finding from Dr. Henderson’s study is that chronic exposure to menthol can change the number of receptors for nicotine in the brain to a similar extent that nicotine can,” says Marina Picciotto. A neuroscientist at Yale University in New Haven, Conn., she did not work on the new study.

“Menthol may increase the addictive properties of nicotine at the molecular level,” Picciotto concludes. Still, she cautions, scientists need to see if that molecular action affects behavior. And to be sure menthol works the same way in people, she says, “We need more information from human subjects.”

Yolks yoke in folks who smoke

Results from a second study presented at the meeting suggest that adding a foul odor to cigarette smoke could help people cut back on smoking. But the idea may work best if people sleep through the stinky experience.

Anat Arzi is a neuroscientist at the Weizmann Institute of Science in Rehovot, Israel. Earlier, she and other researchers had shown that people can learn to link some experiences as they sleep.

Arzi now wondered whether that type of learning might influence waking behaviors, such as smoking. To find out, she and other scientists exposed groups of smokers to different odors. One stinky stew mixed together the stench of cigarette smoke and rotten eggs. Another paired the smells of smoke and rotten fish.

Researchers told everyone participating in the study that the experience might help them stop or cut back on smoking. But only those smokers who smelled the foul combos while awake knew what just what the experiment involved.

Other smokers smelled those odors only while they slept. Unlike loud noises or bright lights, odors seldom wake people up.

Some volunteers in a study in Israel were exposed to a mix of foul odors and cigarette smoke during different stages of sleep. These tests showed that stinky sleep smells might help people cut back on smoking.

COURTESY OF MICHAEL COOPER.

One group smelled the nasty smells during Stage 2 sleep. That’s the type that occurs most of the night. Others experienced it during rapid eye movement (REM) sleep. Most dreams occur during REM sleep. The study also included control groups — people who slept while no smells scented the air.

Over the following week, people in each group tracked how much they smoked. People exposed to noxious smells during Stage 2 sleep smoked significantly less than before.

“The reduction was around 30 percent,” Arzi reported. That group smoked significantly fewer cigarettes on each day during the week, too.

In contrast, people treated during REM sleep smoked significantly less on only two of the next seven days. So here, the effect did not seem to last all week. And the group that had been awake when exposed to the odors? They showed no change in their smoking habits.

“In other words, sleep learning can influence later awake behavior,” Arzi concludes. The Journal of Neuroscience published the study by Arzi and her colleagues in November.

“The most significant finding of Dr. Arzi’s study is that pairing a nasty odor with the smell of a cigarette can reduce the amount of smoking for several days — and that this only happens during sleep,” says Picciotto, the Yale neuroscientist.

Arzi’s study paired odors for just one night. It then tracked smoking for only one week afterward. A next step, says Picciotto. “would be to see how long the effect lasts.”

That’s important, because tobacco addiction is a major health problem. In the United States alone, cigarette smoking leads to roughly one in five early deaths each year. That statistic comes from the National Institute on Drug Abuse in Rockville, Md. What’s more, it notes, roughly 85 percent of smokers fail when they try to stop on their own.

For that reason, scientists need to learn all they can about causes and treatments for tobacco addiction. The new studies on smoking and smelly substances could one day help all of us breathe easier.

Power Words

addiction The uncontrolled use of a habit-forming drug or uncontrolled and unhealthy habit (such as video game playing or phone texting). It results from an illness triggered by brain changes that occur after using some drugs or engaging in some extremely pleasurable activities. Persons with an addiction will feel a compelling need to use a drug (which can be alcohol, the nicotine in tobacco, a prescription drug or an illegal chemical such as cocaine or heroin), even when the user knows that doing so risks severe health or legal consequences. (For instance, even though 35 million Americans try to quit smoking each year, fewer than 15 out of 100 succeed. Most begin smoking again within a week, according to the National Institute on Drug Abuse.)

chronic A condition, such as an illness (or its symptoms, including pain), that lasts for a long time.

control A part of an experiment where nothing changes. The control is essential to scientific experiments. It shows that any new effect must be due to only the part of the test that a researcher has altered. For example, if scientists were testing different types of fertilizer in a garden, they would want one section of to remain unfertilized, as the control. Its area would show how plants in this garden grow under normal conditions. And that give scientists something against which they can compare their experimental data.

dopamine A neurotransmitter, this chemical helps transmit signals in the brain.

fluorescent Capable of absorbing and reemitting light. That reemitted light is known as a fluorescence.

inert Inactive or having no chemical or physical effects.

neuroscience Science that deals with the structure or function of the brain and other parts of the nervous system. Researchers in this field are known as neuroscientists.

neurotransmitter A chemical substance that is released at the end of a nerve fiber. It transfers an impulse to another nerve, a muscle cell or some other structure.

nicotine A colorless, oily chemical produced in tobacco and certain other plants. It creates the ‘buzz’ effect associated with smoking. It also is highly addictive, making it hard for smokers to give us their use of cigarettes. The chemical is also a poison, sometimes used as a pesticide to kill insects and even some invasive snakes or frogs.

nicotinic receptors A group of brain proteins that affects the signaling of dopamine. Repeated exposure to nicotine leads to more of these receptors in particular areas of the brain.

REM sleep A period of sleep that takes its name for the rapid eye movement, or REM, that occurs. People dream during REM sleep, but their bodies can’t move. In non-REM sleep, breathing and brain activity slow, but people can still move about.

ventral tegmental area Part of the midbrain. It plays an important role in thinking, motivation, emotions and addiction.

WASHINGTON — In the late 2000s, a new class of street drugs emerged that were quickly nicknamed “bath salts.” Their name reflected the fact that they looked like small salt-like crystals. Because they were not initially regulated, many teens and others saw them as a “legal” way to get high. That changed in 2011, when U.S. government ruled them illegal. Still, many people continue to use them. A new study now shows why that’s bad. These drugs reduce the ability of different brain regions to communicate, at least in rats.

The finding may explain the paranoia, delirium and aggression that some users of bath-salt drugs experience.

The brain relies on a flow of communications between its different parts. That’s how it processes information. In tests on rats given one type of bath salts, communication levels fell among the 86 brain regions studied.

“The higher the dose, the less connectivity you get in the brain,” concludes neuroscientist Marcelo Febo. “It causes a pretty global reduction.” Febo presented his team’s findings here, on November 15, at the annual meeting of the Society for Neuroscience.

Bath salts work by boosting levels of dopamine (DOPE-uh-meen). It is a messenger molecule related to feelings of reward and pleasure. The drugs also raise levels of norepinephrine (NOR-ep-ih-NEFF-rin) and serotonin (SAYR-uh-TOW-nin). These two brain chemicals are also messengers. They play roles in attentiveness and mood.

Low doses of bath salts can make users feel euphoric and alert. However, things can change just hours after taking one variant, called MDPV (short for 3,4-methylenedioxypyrovalerone). Some users experience a powerful crash. The effects can be unpredictable and dangerous. Users may grow delirious, suicidal or violent.

Febo and his team wanted to investigate the lingering effects of bath salts on the entire brain. The researchers gave doses of either MDPV or salt water to 46 laboratory rats. The experts then waited an hour before scanning the rats’ brains with functional MRI. This special machine uses strong magnetic fields to study brain activity. Among the brain regions in rats given MDPV, levels of synchronized activity dropped broadly.

That change may explain the erratic behavior seen in some people who take bath salts, said Febo, of the University of Florida in Gainesville. The same effect also can occur in people who chronically abuse cocaine and other drugs, he added.

Febo’s team must still compare the effects of MDPV to those of other chemically related stimulants. These include amphetamine (am-FET-uh-meen) and cocaine. So far, attempts to scan the brains of rats dosed with cocaine made the animals too unstable to obtain results.

Without a comparison, the data lack context, said Michael Baumann. He is a neuroscientist at the National Institute on Drug Abuse in Baltimore, Md. “They’re really big findings,” he said. “But the question is, ‘Do other stimulants do this?’ Or is it unique to bath salts?”

Bath salts have nothing to do with bathing. The nickname for this family of drugs comes from their resemblance to the Epsom salt crystals sprinkled in bathwater.

Power Words

amphetamines Potent drugs that stimulate the brain. They can be used as a medicine to treat attention deficit hyperactivity disorder (ADHD) or other types of disease. However, these can be habit forming (somewhat addictive) and in high doses can provide euphoria, delirium and other symptoms similar to cocaine.

bath salts The common name, or street name, given to a class or illegal drugs. They get their name from their resemblance to the Epsom salt crystals that some people sprinkle in bathwater to soothe sore muscles.

context The setting or circumstances that help explain an event, some statement or some conclusion.

delirium A symptom of mental upset where people become seriously confused or out of touch with what’s happening in their environment. They may no longer realize where they are, how they got there or what’s happening to them. Fevers, some drugs and some sorts of mental illness can all trigger temporary periods of delirium.

dopamine A neurotransmitter, this chemical helps transmit signals in the brain.

erratic An adjective that describes omething that happens at unpredictable intervals or a behavior that is unpredictable.

fMRI (functional magnetic resonance imaging) A special type of machine used to study brain activity. It uses a strong magnetic field to monitor blood flow in the brain. Tracking the movement of blood can tell researchers which brain regions are active. (See also, MRI or magnetic resonance imaging)

neuroscience Science that deals with the structure or function of the brain and other parts of the nervous system. Researchers in this field are known as neuroscientists.

norepinephrine A type of stress hormone secreted by the adrenal glands. It constricts blood vessels. It also increases the force and rate at which the heart contracts.

paranoia The feeling of persecution — that people are out to “get” you — or that other people cannot be trusted. It can cause the affected person to feel intense anger, hatred or a sense of betrayal.

serotonin A chemical present in blood that constricts blood vessels and communicates signals in the brain and nervous system.

stimulant Something that triggers an action. (in medicine) Drugs (including caffeine) that can stimulate the brain, triggering a feeling of more energy and alertness. Some dangerous illegal drugs can do this too, such as cocaine.

unique Something that is unlike anything else; the only one of its kind.

variant A version of something that may come in different forms. (in biology) Members of a species that possess some feature (size, coloration or lifespan, for example) that make them distinct. (in genetics) A gene having a slight mutation that may have left its host species somewhat better adapted for its environment.